1. Field of the Invention
The present invention relates to semiconductor devices and methods for manufacturing semiconductor devices. More particularly, the invention relates to a semiconductor device in which semiconductor materials having different lattice constants are epitaxially grown in recessed portions at the sides of gate electrodes and a method for manufacturing the same.
2. Description of the Related Art
In semiconductor devices provided with MOS transistors, techniques that improve carrier mobility by application of stress to channel regions of a semiconductor substrate have been actively used. As one of such techniques, use of a structure shown in FIG. 11 has been proposed. In this structure, the surface of a semiconductor substrate 101 is isolated by isolation films 102, and gate electrodes 104 are disposed so as to extend across an isolated active region 103, and recessed portions are provided at both sides of the gate electrodes 104. Epitaxial layers 105 composed of a semiconductor material having a different lattice constant from that of the semiconductor substrate 101 are disposed in the recessed portions, and serve as source/drain regions.
In such a case, for example, in p-type MOS (PMOS) transistors, silicon germanium (SiGe) having a larger lattice constant than silicon (Si) constituting the semiconductor substrate 101 is grown into the epitaxial layers 105. Thereby, compressive stress is applied to channel regions ch, and the carrier mobility is improved. For example, refer to Japanese Unexamined Patent Application Publication No. 2006-165012 (Patent Document 1).
Meanwhile, in n-type MOS (NMOS) transistors, silicon carbon (SiC) having a smaller lattice constant than silicon (Si) constituting the semiconductor substrate 101 is grown into the epitaxial layers 105. Thereby, tensile stress is applied to channel regions ch, and the carrier mobility is improved. For example, refer to Kah Wee Ang, et al., “Enhanced Performance in 50 nm N-MOSFETs with Silicon-Carbon Source/Drain Regions”, Dec. 2004, IEDM Tech. Dig., 1069-1071 (Non-patent Document 1).